The present invention relates to fluid pressure controllers and particularly controllers of the type which provide a regulated output signal when connected to a source of variable fluid pressure and which are responsive to a mechanical input to alter the desired value of the regulated output signal. Devices of this type are employed in accessory controls for internal combustion engines in automotive applications where it is desired to provide a regulated and selectively changeable fluid pressure vacuum signal responsive to movement of the engine throttle and also to provide for the completing and the breaking of an electrical circuit at a predetermined position of the mechanical input such as the vehicle throttle position. An example of such an application is a vacuum controller which provides a regulated vacuum signal, upon connection to the vacuum pump source and receives an input from the vehicle throttle to provide changes in the regulated vacuum output signal in accordance with the predetermined scheduled throttle position for actuating an exhaust gas recirculation control valve. The electrical circuit which is completed and broken at predetermined throttle position may be employed to actuate and de-actuate an electrically operated transmission shift control mechanism.
It is known to provide a rotary cam for adjusting the bias force on a pressure force-balance type vacuum modulator valve for adjusting the level of a regulated vacuum output signal. An example of such a device is that shown and described in U.S. patent application Ser. No. 88,806 filed Oct. 29, 1979, in the names of R. J. Franz, V. DeVera and J. Dahlstrom and assigned to the assignee of the present application. The aforesaid Franz et al. application employs a rotating cap which engages an annular helical cam disposed therewithin for effecting axial movement of the cam to vary the preload on a tension spring connected to provide a variable bias on a pressure responsive modulator valve for providing a regulated vacuum output signal.
Such devices as that described in the Franz et al. application are employed for providing a regulated vacuum signal from varying source, such as a vacuum pump source, for use in controlling devices such as transmissions and exhaust gas recirculation valves.
Another known vacuum signal controller is that described in U.S. patent application Ser. No. 897,604 filed Apr. 18, 1978, now U.S. Pat. No. 4,245,789 issued Jan. 20, 1981 in the name of R. J. Franz and assigned to the assignee of the present invention. The Franz device utilizes a rotating cam to vary the preload on a temperature sensitive element operated vacuum modulator valve.